To be honest I love both Reborn and Rejuvenation, but I have to admit, that I think Reborn is quite hard playing the first time around. It is also very rewarding, when you finally beat someone you had trouble with before, but you need to be willing to commit quite some hours to the game.
Rejuvenation is similar, but has, as mentioned before, a casual playmode. it is still harder than any official pokemon game but fun anyways.
For both Reborn and Rejuvenation there are many guides and threads available and you can always ask for help in the forum if you are stuck in specific situations.
